Process of dyeing



Patented Nov. 26, 1935 A UNITE-D STATES PATENT OFFICE 2.021.932 PROCESS or DYEING Richard G. Clarkson, Wilmington, Del., and Frank Willard Johnson, Pennsgrove, N. J.. assignors to E. I. du Pont de Nemours & Com-- pa y Wilmington, Del., a corporation of Delaware No Drawing. Application November 1a, 1932, i Serial No. 698,584

12 Claims. (or. 8-5) Other and further objects of this invention will 10' appear as the description proceeds.

In dyeing. with vat dyestuffs, trouble is often experienced due to the fast'rate ofabsorption of the dyestufl on the fiber. Since not all parts of a given piece of cloth, or package of yarn, are exposed to the vat at the same moment, the

first portions to contact the vat get the benefit of a strong vat while some others come in contact with a partially exhausted vat. The result is a spotty and unevenly dyed piece of fabric or package of yarn.

In dyeing with avat dye on a continuous machine, wherein the fabric is run oil a roll, dipped v continuously into a vat and then wound upon another roll or passed through another bath (the re-reducing bath) similar difliculties are experienced. As the fabric passes through the vat, the dye is taken up and the vat is gradually being exhausted. To overcome this, further additions of dyestuii to the bath are necessary. It is clear, however, that unless the subsequent additions of dyestuff are carefully regulated and timed to the 'rate of exhaustion of the vat, cer-- tain parts of the bolt or roll will be dyed stronger than others.

' Then too, in order to obtain the desired shade it is often necessary to use a mixture of dyes whose rates of dyeing are. quite diiferent. Since the fabric remains in the dyebox only a very short time, much less than is required for com-' 40 plete exhaustion, it will be apparent that the more rapid-dyeing color will in this case be exhausted more rapidly and the shade of the dye cloth will change as the roll-proceeds thru the vat. In order to overcome this, it is necessary to make additions of the more rapid dyeing component and constant adjustment is necessary. Such adjustment becomes more diilicult the more difierence there is between the rates of dyeing of the components.

It has accordingly been the custom in the art to add a retardant to the vat. The retardant is an'agent which diminishes the rate of absorption of the dye on the fabric. When dyeing with a plurality of vat dyestuifs, the retardant will generally slowdown the rate of the faster dye relatively more than the rate of slower dye, and will thereby diminish the difference in the dyeing rates of the individual components of .the mixture and facilitate adjustment of the mixture as'the fabric proceeds through the vat. In dye- 5 ing with a single color in the continuous process, the retardant likewise facilitates control of the strength of the vat, thereby rendering the dyeings more uniform.

In package dyeing, the retardant is also bene- 10 ficial' in that it delays exhaustion until practically all portions of the package have become wetted by the coloring solution. The result is improved penetration and more level dyeings.

As such retardants in the art, soap and glue 15 have been employed. The operation of these, however, is not always satisfactory. In the first 7 place the degree of retardation is relatively small; in thesecond place there are many dyestuffs as .to which the mentioned retardants fail alto- 20 gether.

' We have now found that cellulose ethers which are soluble or dispersible in the vat are excellently adapted for the purpose mentioned.

Their action is generally considerably more marked thanthat of glue or soap, and their range of applicability is much wider.

Any cellulose ether which forms a stable colloidal solution in dilute caustic at dyeing temperatures (from room temperature up toabout 30 0r F.) may be used for our purpose. Among these may be mentioned the various ethers of cellulose which contain in the non-cellulosic radical a group tending to make the moleeule soluble in alkali; for instance, cellulose eth- 35 ers containing in the non-cellulosic radical sulfonic, carboxy orhydroxy groups.

Compounds of this type are described in U. S. Patents 1,722,927 and 1,682,382; see also, Technology ofcellulose ethers by E. C. Worden, vol. 40 3, (Chem. Cat. C0,, New York, 1933). The stage at which the retardant is added is unimportant so long as it is present in the vat or on the fibre during dyeing.

As the simplest and commonest example of 45 a cellulose ether which is soluble in alkaline solution may be mentioned sodium cellulose glycollate. This one is generally prepared from sodium cellulose and the sodium salt of chloroacetic acid.

and is a relatively inexpensive commercial ar- 50 ticle.

Other ethers, however, of cellulose may be employed successfully, provided they are soluble in the .vat without decomposition, for in stance, the ether of cellulose and chloropropionlc acid or its alkali-metal or ammonium salts.

Example I 2.5 parts of trichloro-indanthrone double paste and 2.5 parts of fiavanthrone double paste are mixed with 31.5 parts of 31 B. caustic soda; 214 parts of water are added and the temperature is adjusted to 120 F. 7.5 parts of sodium hydrosulfite are now stirred in. After 15 minutes 160 parts of a 2.5% aqueous solution (or sol) of sodium cellulose glycollate are added and then 1590 parts of water, keeping the temperature of the vat at 120 F. The vat is now ready for dyeing 100 parts of yarn or fabric by any desired process and will be found to give the improved results above discussed. Similar improved results are observable when one uses a mixture of trichloro-indanthrone and the dyestuif described in Example 3 of U. S. P. 1,329,435.

Example II 2.5 parts of a 20% paste of the dyestufl. described in Ex. 3 of U. S. P. 1,329,435 are mixed with 31.5 parts of 31 B. caustic soda and 217 parts water. The temperature is. adjusted to 140 F. and 7.5 parts of sodium hydrosulfite are stirred in. After 15 minutes 100 parts of 2.5% aqueous sodium cellulose glycollate are added and then 1750 parts of water, the temperature being maintained at 140 F. The vat is now ready for dyeing 100 parts (more or less according to the depth of shade desired) of yarn or fabric by any standard process.

Instead of the sodium salt of cellulose-glycollic acid, any other alkali-soluble salt may be employed, for instance, the potassium or ammonium salt. The free acid form of this compound may also be used. The quantity of retardant employed may vary within wide limits. Very marked retardation has been obtained with quantities varying from 1 to 10% by weight based on the weight of the fibre.

It will be understood that the dyes mentioned are only illustrative, since our novel retardant gives excellent results with a great many other vat dyestufis when used individually or in combination.

If desired, the retardant may be sprayed or impregnated upon the fiber instead of adding it to the vat. The latter then maybe prepared of the usual ingredients in the ordinary manner.

Many other variations and modifications are possible in our preferred embodiment above set forth without departing from the spirit of this invention.

As already mentioned above, our invention may be practiced with a cellulose ether which is actually soluble in alkaline medium, or with one which merely gives a stable colloidal solution. Therefore, in the claims below we shall use the expression alkali-dispersible" as a generic term to cover both the property of complete or theoretical solubility and the property of yielding a stable colloidal solution.

We claim:

l. A process of dyeing fiber with a vat dyestuff 5 which comprises applying the dyestufi solution to the fiber in the presence of a cellulose ether which is adapted to be dispersed in alkaline solution.

2. A process of dyeing fiber with a vat dyestufl which comprises applying the dyestufl solution to the fiber in the presence of a cellulose ether which is adapted to form a colloidal suspension or m-- lution in dilute aqueous alkali.

3. A process of dyeing fiber with a vat dyestuf! which comprises applying the dyestufi solution to the fiber in the presence of a cellulose ether which is a protective colloid and is soluble in.

alkali. v v

4. A process of dyeing fiber with a vat dyestufi which comprises applying the dyestuff solution to the fiber in the presence of a cellulose other which carries in the non-cellulosic radical a group tending to make'the molecule soluble in alkali.

5. A process of dyeing fiber with a vat dyestuff which comprises applying the dyestuif solution to the fiber in the presence of a ceilulom ether which contains a solubilizing radical selected from the group consisting of sulfo, carboxy and hydroxy. 1

6. A process of dyeing fiber with a vat dyestufl which comprises applying the dyestuff solution to the fiber in the presence of cellulose-glycollic compound selected from the group consisting of the free acid and an alkali-soluble salt thereof. 35

7. A process of dyeing fiber with a vat dyestuif which comprises applying the dyestufi solution to the fiber in the presence of sodium cellulose glycollate.

8. In the process of dyeing fabric with a vat w dyestuff by the continuous process, the improvement which comprises incorporating into the dye bath an alkali-dispersible ether of cellulose.

9. In the process of dyeing fabric with a vat .dyestuif by the continuous process, the improvement which comprises incorporating into the dye bath the cellulose ether of glycollic acid or a water soluble salt thereof.

10. In the process of dyeing fabric with a plurality of vat dyestuffs the improvement which comprises effecting the dyeing in the presence of an alkali-dispersible ether of cellulose.

11. In the process of dyeing fabric with a plurality of vat dyestuifs the improvement which comprises effecting the dyeing in the presence of a salt of cellulose glycollic acid.

12. A retardant for vat dyestuffs which comprises a cellulose-glycollic compound selected from the group consisting of the free acid and alkali-soluble salts thereof as principal ingrew dient.

RICHARD G. CLARKSON. F. WILLARD JOHNSON. 

